Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
h,w=map(int,input().split())
a=[]
for i in range(h):a.append(list(input()))
white=[flatten for inner in a for flatten in inner].count(".")
turn=1
a[-1][-1]=1
while turn in [flatten for inner in a for flatten in inner]:
    for i in range(h):
        for j in range(w):
            if a[i][j]==turn:
                if i>0 and a[i-1][j]==".":a[i-1][j]=turn+1
                if i<h-1 and a[i+1][j]==".":a[i+1][j]=turn+1
                if j>0 and a[i][j-1]==".":a[i][j-1]=turn+1
                if j<w-1 and a[i][j+1]==".":a[i][j+1]=turn+1
    turn+=1
    if a[0][0]!=".":break
print(-1 if a[0][0]=="." else white-a[0][0])